Post on 16-Dec-2015
The Java Foundation Classes (JFC) are a set of packages encompassing the following APIs: Abstract Window Toolkit (AWT): native
GUI components Swing: lightweight GUI components 2D: rendering two-dimensional shapes, text,
and images Accessibility: allowing compatibility with, for
example, screen readers and screen magnifiers
Provides basic UI components: Buttons, lists, menus, textfields, etc Event handling mechanism Clipboard and data transfer Image manipulation Font manipulation Graphics
Platform independence is achieved through peers, or native GUI components
java.awt Basic component functionalityjava.awt.accessibility Assistive technologiesjava.awt.color Colors and color spacesjava.awt.datatransfer Clipboard and data transfer supportjava.awt.dnd Drag and dropjava.awt.event Event classes and listenersjava.awt.font 2D API font packagejava.awt.geom 2D API geometry packagejava.awt.im Input methodsjava.awt.image Fundamental image manipulation classesjava.awt.peer Peer interfaces for component peersjava.awt.print 2D API support for printingjava.awt.swing Swing components
The first AWT (Java 1.0) was rolled out in an incredible 6 weeks using peers
Thus an AWT menu on the Solaris platform, for example, actually creates a Motif menu object as its peer
UI components that have peers are called heavyweight because they are rendered in their own (opaque)
windows and thus are expensive to use, they must be rectangular and cannot have
transparent backgrounds, and they are not amenable to being subclassed
Java Program
Java AWT
NativeWindowSystemPeers
A Java program creates and displays an AWT component,which creates and displays a native component, or peer.
AWT 1.1 introduced the notion of lightweight components which: are contained within a heavyweight
component's window do not have peers are rendered in their container's window
rather than one of their own do not incur performance penalties and can
have transparent backgrounds Almost all Swing components are
lightweight ones that extend either java.awt.Component or java.awt.Container
Object
Component
Container ButtonList
Scrollbar
Label
Canvas
WindowJComponent
Scrollpane
Swing does not replace the AWT; it is built on top of it
All 1.0 AWT components are heavyweight; corresponding Swing components are lightweight
Swing component names begin with ``J'': Component (AWT) vs. JComponent (Swing) Button (AWT) vs. JButton (Swing)
Always use Swing components; however, since Swing is built on top of AWT, you will need to know some AWT methods
JComponent
AbstractButton
JButton JMenuItem
JToggleButton
JCheckBox
JLabel
JList
JScrollBar
JFileChooser
Note that JComponents are containers JComponents do not extend their AWT
counterparts: For example, the JButton class is not a
subclass (direct or indirect) of Button However, some Swing components are
not JComponents For example, some Swing containers are
direct subclasses of their AWT counterparts
Container
JComponent Panel
ScrollPane
Window
Dialog Frame
Applet
Container
JComponent Panel
ScrollPaneWindow
Dialog Frame Applet
JDialog
JWindow
JFrame JApplet
JComponent
JLayeredPane JPanel
JScrollPane
JInternalFrame
JDesktopPane
JTable
JTree
void setBackground(Color c) void setForeground(Color c) void setEnabled(boolean b) void setVisible(boolean b) void setFont(Font f) void setSize(Dimension d) void setLocation(int x, int y)
All but setSize and setLocation are overridden by the JComponent class.
import java.awt.*;import javax.swing.*;
public class SwingTest {
public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); frame.setVisible(true); }
}
setSize and setLocation require java.awt.*; the rest require javax.swing.*
The JFrame constructor argument is used as a title The Dimension constructor takes an integer width
and height, respectively The setLocation method takes a pair of integer
coordinates (x,y) where (0,0) is the upper left corner of the display
The visibility of a JFrame is set to false by default
This window was managed by the K Desktop Environment (KDE)
Clicking the Close button (X) will cause the display to be hidden, but the program will continue since no listeners are set up yet
Can use ctl-C to kill the Java Virtual Machine
Color.black Color.blue Color.cyan Color.darkGray Color.gray Color.green Color.lightGray
Color.magenta Color.orange Color.pink Color.red Color.white Color.yellow
The java.awt.Color class has the following staticfields (data members):
import java.awt.*;import javax.swing.*;
public class SwingTest {
public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); contentPane.setBackground(Color.red); frame.setVisible(true); }
}
Q: Why not just: frame.setBackground(Color.red); ?
A: In order to be lightweight, Swing's top-level window objects must be built on top of a lightweight AWT Container object introduced in version 1.1
This container is called a content pane Swing top-level window classes:
JWindow JFrame JApplet JDialog JInternalFrame
import java.awt.*;import javax.swing.*;
public class SwingTest {
public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE IS A LABEL"); contentPane.add(label, BorderLayout.NORTH); JButton button = new JButton("BUTTON"); contentPane.add(button, BorderLayout.SOUTH); frame.setVisible(true); }
}
Resized
Since the frame is a top-level Swing window, components must be added to its content pane
When components are added to a container, how they are placed is dependent upon the container's layout manager
The default layout manager for a JFrame is a BorderLayout manager (described later)
When adding to a container whose layout manager is BorderLayout, the second parameter should be a location defined in the BorderLayout class
import java.awt.*;import javax.swing.*;
public class SwingTest {
public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE IS A LABEL"); contentPane.add(label, BorderLayout.NORTH); JButton button = new JButton("BUTTON"); contentPane.add(button, BorderLayout.SOUTH); String[] options = {"Option 1", "Option 2", "Option 3"}; JList list = new JList(options); contentPane.add(list, BorderLayout.CENTER); frame.setVisible(true); }}
Note that "Option 3" has been selected.
public class SwingTest {
public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(400,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE IS A LABEL"); contentPane.add(label, BorderLayout.NORTH); JButton button = new JButton("BUTTON"); contentPane.add(button, BorderLayout.SOUTH);
String[] options = {"Option 1", "Option 2", "Option 3"}; JList list = new JList(options); contentPane.add(list, BorderLayout.CENTER);
JCheckBox cbox = new JCheckBox("Check"); contentPane.add(cbox, BorderLayout.WEST);
JSlider slider = new JSlider(); contentPane.add(slider, BorderLayout.EAST);
frame.setVisible(true); }}
A layout manager determines the location and size of components placed into a container
Different layout managers use different algorithms for determining size and location: BorderLayout: places at compass locations and
center FlowLayout: places components in rows, left to right GridLayout: places in rectangular grid BoxLayout: places in a single row or column
public class SwingTest {
public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane();
contentPane.setLayout(new FlowLayout()); JLabel label = new JLabel("HERE IS A LABEL"); JButton button = new JButton("BUTTON"); String[] options = {"Option 1", "Option 2", "Option 3"}; JList list = new JList(options); JCheckBox cbox = new JCheckBox("Check"); JSlider slider = new JSlider(); contentPane.add(label); contentPane.add(button); contentPane.add(list); contentPane.add(cbox); contentPane.add(slider);
frame.setVisible(true); }
}
Resized
The default layout manager for content panes is BorderLayout. Recall that the following Swing components have content panes: JWindow JFrame JDialog JApplet JInternalFrame
The other Swing container is the JPanel, whose default layout manager is FlowLayout.
A JPanel object can be used for grouping components into a container, which can then be added to another container
The JPanel constructor with no arguments creates a panel with a FlowLayout manager
Another JPanel constructor takes any layout manager as an argument
A JPanel can also be used a a blank area for drawing custom graphics
JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE ARE SOME BUTTONS", SwingConstants.CENTER);
JButton button1 = new JButton("BUTTON1"); JButton button2 = new JButton("BUTTON2"); JButton button3 = new JButton("BUTTON3"); JPanel panel = new JPanel(); panel.add(button1); panel.add(button2); panel.add(button3);
contentPane.add(label, BorderLayout.NORTH); contentPane.add(panel, BorderLayout.CENTER);
frame.setVisible(true);
Note use of SwingConstants.CENTER argumentin JLabel constructor.
JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE ARE SOME BUTTONS", SwingConstants.CENTER);
JButton button1 = new JButton("BUTTON1"); JButton button2 = new JButton("BUTTON2"); JButton button3 = new JButton("BUTTON3"); JPanel panel = new JPanel(); panel.setLayout (new BoxLayout(panel, BoxLayout.Y_AXIS)); panel.add(button1); panel.add(button2); panel.add(button3);
contentPane.add(label, BorderLayout.NORTH); contentPane.add(panel, BorderLayout.CENTER);
frame.setVisible(true);
The button panel is to the west because no other component was placed there
The BoxLayout constructor requires both the component being laid out and either: BoxLayout.X_AXIS BoxLayout.Y_AXIS
Some layout constructors allow hgap and vgap, integers specifying the number of pixels separating components horizontally and vertically
FlowLayout allows the specification of whether the line of components should be left-justified, right-justified, or centered
new FlowLayout(int align)new FlowLayout(int align, int hgap, int vgap)
new BorderLayout(int hgap, int vgap)
new GridLayout(int rows, int cols)new GridLayout(int rows, int cols, int hgap, int vgap)
JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); LayoutManager lm = contentPane.getLayout(); ((BorderLayout)lm).setHgap(25);
JLabel label = new JLabel("HERE ARE SOME BUTTONS", SwingConstants.CENTER);
JButton button1 = new JButton("BUTTON1"); JButton button2 = new JButton("BUTTON2"); JButton button3 = new JButton("BUTTON3"); JPanel panel = new JPanel(); panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); panel.add(button1); panel.add(button2); panel.add(button3);
contentPane.add(label, BorderLayout.NORTH); contentPane.add(panel, BorderLayout.CENTER);
frame.setVisible(true);
The LayoutManager returned by getLayout() is an interface type that the BorderLayout class implements
The setHgap method we want is in the BorderLayout class
So we must cast the LayoutManager to BorderLayout in order to use setHgap
Layout managers often need to resize their components to make things fit For example, the widths and heights of
components in a BoxLayout are adjusted according to both preferred and maximum heights and widths
If you don't like the size of the components a layout manager comes up with, you may have to give sizing hints using the following methods from the JComponent class: void setMinimumSize(Dimension d) void setPreferredSize(Dimension d) void setMaximumSize(Dimension d)